1. Field
The present invention relates to a greening system enabling plants to effectively grow with only minimal natural rainfall or limited irrigation even in the absence of any particular irrigator by making use of water absorbing and releasing capabilities of porous structures such as charcoal perforated with continuous fine capillary tubes, advantageously applicable to greening of roofs, surroundings of buildings, upper surfaces of underground structures, paved streets and/or areas usually lacking in greenery.
2. General Background
As needed for better urban environments, rooftop gardening is increasingly become more in demand with each passing year, not only for the purpose of making existing buildings more energy-efficient as a whole thanks to roof thermal insulation and greater aesthetics but also as expected, to contribute to the achievement of milder climates throughout urban centers thanks to latent heat of gasification associated with transpiration of plants.
However, the conventional method of rooftop greening has traditionally required large-scale structural reinforcement in many cases for existing buildings to bear increased loads associated with massive amounts of soil needed on the rooftop surface, also costing considerably for waterproofing of the roof structure which is permanently supplied with water while preventing future leakage problems.
On the other hand, the layer is much thinner, even with a larger amount of soil than typically found on the ground, losing water much more quickly by evaporation and indispensably requiring irrigation to supply water quite insufficient only from natural rainfall for plants to grow all over the area of rooftop greening.
To realize a greening system with a minimized load on a building, free from risk of leakage and easily irrigated, different methods for rooftop greening have been proposed, making use of planters widely used to grow vegetation anywhere in the absence of gardening soil (e.g. on rooftop, veranda, and paved zones). Greening systems using such planters are structured as disclosed in the following patent documents 1 and 2:    Document 1: Japanese Patent Application Laid Open to the public (KOKAI) No. 9-140252 (see pages 1 to 6, FIGS. 1 to 3); Document 2: Japanese Patent Application Laid Open to the public (KOKAI) No. 10-108547 (see pages 1 to 6, FIGS. 1 to 5).
The conventional greening systems using planters have been installed directly on rooftops or in planter carriers in general. Planters loaded with a limited amount of soil within the container, are easily handled, weigh relatively little, have lower waterproofing costs thanks to the waterproofing capacity of the same planters, and are free from the risk of leakage typically caused by roots breaking into the roof slab.
On the other hand, artificial materials such as gravel or foamed bricks can be chosen instead of natural soil for the so-called “hydro-culture” in the field of indoor gardening with planters for vegetation to grow in any everyday containers. Plants should essentially be supplied with oxygen and water at roots sufficiently enough to avoid root rot or water spot. Plants in planters, perforated for outflow of water exceeding the necessity for roots, are free from the risk of root rot but indispensably need to be frequently irrigated, as lacking in water retention.
On the other hand, plants in hydro-culture can grow, as watered at relatively long intervals (e.g. once every few weeks) but it is important for imperforate containers to split artificial cultivation soil appropriately into the gas and liquid phases, requiring an initial water level strictly adjusted in accordance with kinds of plants and chemical agents to be administered at bottom of each container to prevent root rot or water spot.
To facilitate adjustment of water level in hydro-culture, different containers for indoor gardening have been proposed, as represented by a pot of double or separable structure to have an outer or lower container as a reservoir. Containers for indoor gardening intended for plants in pot culture to be prevented from death or root rot as watered and drained appropriately by bottom irrigation have been proposed by hydro-culture as disclosed e.g. in the following patent documents 3 and 4:    Document 3: Japanese Patent Application Laid Open to the public (KOKAI) No. 5-219845 (see pages 1 to 7, FIGS. 1 to 9); Document 4: Japanese Patent Application Laid Open to the public (KOKAI) No. 8-140507 (see pages 1 to 6, FIGS. 1 to 6).
The above Document 3 discloses an irrigator comprising a bowl with a hole opened at bottom to contain a plant and soil, a saucer to retain water and a bibulous wick to suck up water into the bowl with capillarity, while the above Document 4 discloses a plant cultivator with an irrigator supplying a bowl with water from a basin placed on the lower face.